...but what if you are using a imported style, is it likely to mess up what
you've saved?

No it won't mess up what you've saved Derek
When you set up a Registration using an 'Imported' Style - assuming you mean one which is in the Composer, rather than a built-in style - just set up the Registration as normal, using the Composer Style or Styles and when you save to SD Card, make sure that 'COMPOSER' is set to 'YES' on Page 2 of the Save operation.